Method of applying lacquer or the like



June 1932- R. z. HOPKINS ET AL 1,861,475

METHOD OF APPLYING LACQUER OR THE LIKE Filed April 27, 1929 43 I m m am/12E023. RCLQ JQZAW 3 0 YWIW Patented Juno 7, 1932 UNITED STATES PATENTOFFICE RALPH Z. HOPKINS AfND WILLIAM D. OGDEN, OF DETROIT, MICHIGAN,ABSIGNOBB TO HUDSON MOTOR GAB COMPANY, 013 DETROIT, MICHIGAN, ACORPORATION O! 6 that of an automobile body.

MICHIGAN METHOD OF APPLYING LAOQUER. OR THE Application fled April 27,

This invention relates to the art of socalled spray painting, andparticularly to the atomization of paint or lacquer and its applicationto a surface to be coated, such as Heretofore it has been-customary, inapplying paint to automobile bodies by spray devices, or so-called sprayguns, to employ compressed air as a means for atomizing or Th reducingthe paint into fine particles or comminuted condition and also as acarrying medium in spraying it 'onthe surface of the body.

Upon general adoption of the so-called spray gun for spray-paintingautomobile bodies, resulting in large economies due largely to thespeeding up of this work, compressed air was used to considerableadvantage as a combined atomizing and carrying medium, enabling thepaint to be properly directed in a finely divided mist.

The use of compressed air as an atomizing and carrying medium, however,has the disadvantage, particularly when employed in connection with thelacquer now extensively used, of producing what is called a dry spray,and in causing orange peel. Due to the fact that a great amount of airis in the spray, when compressed air is used, an entirely smooth anduniform surface cannot always be obtained, and frequently air cells orpockets are formed in or under the lacquer coating which eventuallyproduces a' peeling condition. Under present day conditions it is thepractice to use to a considerable extent lacquers having a substantialpercentage of volatile constituents or solvents which evaporate rapidlywhen exposed to the air. In using compressed air as an atomizing medium,and its consequent intimate admixture with the atomized liquid, thisevaporation is very marked, causing what is termed a relatively dryspray. We have found that by eliminating the use of compressed air amuch smoother coating is provided; the tendency to orange-peel? has beenminimized very noticeably; and the evaporation of the lacquer beforestriking the surface to be painted is less pronounced, thereby enablingus to produce a Wetter coating.

1929. Serial No. 358,584.

In accordance with the primary feature of the present invention,theliquid lacquer or the like is atomized mechanically, and without thedirect action of compressed air thereon or its admixture therewith, asby subject- It; mg 1t to the action of centrifugal force, and a spray ofthe atomized liquid is directed and deposited upon the surface to becovered.

e spray thus produced mechanically, as by centrifugal action, or bymeans of a high 00 pressure nozzle, and which therefore tends to fly inall directions, is, in accordance with another feature of the invention,so controlled and directed upon the work as to eliminate waste. Thischange in the normal direction of movement of the spray is preferablyaccomplished by projecting a hollow jet or stream of compressed air fromthe gun in the direction of the work and surrounding the spray, so as toform in a sense a sheath or envelope which encloses the spray and causesit to follow a certain course. The compressed air does not constitute anatomizing medium, nor does it even form a carrying medium in the usualsense, in that there is no intimate admixture thereof with the atomizedlacquer, but is merely a guiding medium for the lacquer, and in use thecompressed air has the further advantage of facilitating drying of thelacquer after it has 30 been applied to the surface.

The invention will best be understood from the following description ofthe construction and operation of certain forms of apparatus by which itmay be practiced, reference being had to the accompanying drawing inwhich: Fig. 1 is a sectional view illustrating one form of spray gun ordevice operating in accordance with the invention. Fig. 2 is a sectionalview showing another form of spray gun by which the invention may bepractice The spray device is shown herein as of the portable type,commonly called a' spray 06 gun, and is constructed so that it can bereadily handled by the workman at'the job, such as in paint-sprayingautomobile bodies. It is important, therefore, in this connection thatthe gun be relatively small, light and mo I compact, and capable ofbeing moved at will from point to polnt.

Referring to Fig. 1 the device may comprise a suitable casing A whichmay be 1n the form of a single casting providing a housing 9 and aremovable ack plate 10. The casting at one side thereof is preferablyprovided with a handle (not shown) to permit the workman to grasp thedevice. The casing 9 may be provided at the front face thereof with anintegral projection or boss 11, the walls of which form a jacketenclosing an annular compressed air chamber 12. The outer wall of thismember 11 is drilled and counterbored to receive the end of a flexibletube or pipe 13 which supplies air to the chamber 12 from a source ofsupply, such as a pump, which forces air'under pressure through theflexible connection 13 into the chamber 12. The inner annular face 11aof the boss 11 is tapered to flare outwardly, this wall being preferably-conical in shape.

Located within the conical chamber 11a is an atomizing cup 14, of whichthe outer wall 146 tapers outwardly and is'parallel.

to the wall 11a and spaced therefrom to provide an air space15-terminating in an annular discharge orifice 15a around the outer edgeof the cup 14. The member 14 is chambered at 14c the walls of whichpreferably flare outwardly. The compressed air chamber 12 communicateswith the passage 15 by means of a series of ducts 16. From thisconstruction it will be seen that the compressed air in the chamber 12will escape through the small ducts or ports 16 into the passage 15which surrounds the atomizing device and which has a discharge orificeor outlet 15a preferably surrounding the discharge mouth of theatomizing cup 14.

The atomizin device 14 is carried at the end of a shaft 17 journalled inthe rear wall 10 and an intermediate wall 18 of the casing. This shaftcarries a small gear 19 in mesh with a large gear 20, the latter beingcarried by a shaft 21 journalled in the casing walls 10 and 18. Theshaft 21 is .a'fiexible shaft and is operated from a suitable electricmotor so as to operate the gearing and drive the shaft 17 at high speed,such as about 10,000 R. P. M. The shaft 17 is drilled centrally toreceive a tube 22 which projects somewhat into the chamber 14a of thespray device 14. This tube extends entirely'through the shaft 17 andcommunicates with a hole 23 drilled through a boss 24 projecting fromthe rear wall 10 of the casing. This boss is counterbored and tapped toreceive a coupling member 25 to which is connected a flexible tube 26for supplying the liquid lacquer.

In the operation of the device above described in accordance with theinvention, the liquid lacquer may be force fed in the proper amountthrough pipe 26 whence it is fed centrally through the shaft 17 into therotary cup 14. The inner wall 14a of the cup picks up the lacquer fromthe end of the tube 22. It will be seen that as the device 14 rotates athigh speed the lacquer will travel outwardly along the flaring face 14aand will be discharged from the device in comminuted or atomizedcondition. The lacquer, or other liquid, will be discharged from thespray device in a fine mist or spray, and a part of this spray normallywill be thrown outwardly and laterally in a direction shown by the arrow27. The compressed air however issuing from the orifice 15a will form asheath or wall substantially in the shape of a cone, as indicated at 28.This air sheath, While of such a form as not to cause substantialadmixture of the air with the atomized lacquer, will direct and guidethe spray in the manner shown at 29 so that it may be properlycontrolled in coating the surface 30.

Referring to Fig. 2, the device illustrated therein comprises a casing31 having a projecting portion or boss 32 provided with an annularcompressed air chamber 33. The inner wall 32a is outwardly tapered orflaring and is suitably spaced from the outer parallel face 33a of arotary cup 330 so as to provide an air passage 34. The construction inthis respect is similar to that described above in connection withFig. 1. The compressed air chamber 33 communicates with the air passageor space 34 by means of a series of small air ducts or ports 35.Compressed air is supplied to the chamber 33 by means of a flexibleconduit 36. The rear face of the cup member 330 is chambered at 37, andthis chamber communicates with the face 336 of the cup by means of aseries of ducts 38. A pipe 39 is carried by the casing and terminateswithin the chamber 37. This pipe is connected by a flexible tube 40 witha suitable source of lacquer supply, whence the lacquer is force fedthrough pipes 40 and 39 to the device. It will be seen that as thelacquer is discharged from the end of the pipe 39 it will be picked upin the groove 41, and held therein by centrifugal action, beingdischarged therefrom through the duct-s 38.

The cup shaped device 330 is carried by the armature shaft 42 of a highspeed electric motor 43 which is also mounted in the casing 31. Thismotor is supplied with current by means of a flexible cable (not shown)from a source of electrical energy.

The device illustrated in Fig. 2 operates to atomize and apply thelacquer spray in substantially the same manner as described above inconnection with that shown in Fig. 1. Air is pumped under pressurethrough the tube 36 into the compressed air chamber 33. Thence thecompressed air esca es through the ducts 35 into the outwardly ar ingpassage 32a which surrounds the atomizing cup 330. The latter isoperated at a very high speed and breaks up the lacquer into minuteparticles by centrifugal action. As described above the spray or mist,thus formed and projected from the rotary cup, is formed into a streamand properly directed substantially in the manner shown in Fig. 2 uponthe surface 30 to be painted by means of the enveloping stream or jet ofcompressed air.

We claim: I

1. The hereindescribed method of applying lacquer or the like to asurface to be coated thereby which consists in atomizing the liquidlacquer mechanically and directing a spray of the atomized lacqueragainst said surface by enclosing the same in an envelope or hollow jetof compressed air while so controlling the form of said jet as to avoidsubstantial admixture of the air with the atomized lacquer.

2. The hereindescribed method of applying lacquer or the like to asurface to be coated thereby which consists in atomizing the liquidlacquer without the direct action of compressed air thereon or itsadmixture therewith and directing a spray of the atomized lacqueragainst said surface by enclosing the same in an envelope or hollow jetof compressed air while so controlling the form of said jet as to avoidsubstantial admixture of the air with the atomized lacquer.

3. The hereindescribed method of applying lacquer or the like to asurface to be coated thereby which consists in atomizin the liquidlacquer by centrifugal action an directing a spray of the atomizedlacquer against said surface by enclosing the same in an envelope orhollow jet of compressed air while so controlling the form of said jetas to avoid substantial admixture of the air with the atomized lacquer.

In testimony whereof we aifix our signatures.

RALPH Z. HOPKINS. WILLIAM D. OGDEN.

